1. Field of the Invention
This invention relates to a rectangular shield excavating machine for use in construction of a tunnel, a hole, a channel or the like having a quadrangular shape in section.
2. Description of the Prior Art
As one of rectangular shield excavating machines for excavating a tunnel having a quadrangular shape in section, there is disclosed a rectangular shield excavating machine using excavating means composed of a plurality of support rods disposed at an interval on a front portion of a quadrangularly tubular shield body so as to be capable of being linearly reciprocated in the direction orthogonal to an axis of the body and a plurality of cutter bits mounted on each support rod. (See Japanese Patent Public Disclosure (KOKAI) No. 1-310089)
In this excavating machine, the inside of the body is divided into a front area maintained at high pressure and a rear area maintained at atmospheric pressure through a partition wall, and the support rod is movably supported by a support plate disposed in the front area in parallel to the partition wall. This excavating machine excavates a facing by the linear reciprocating motion of each cutter bit with the linear reciprocating motion of the support rod.
As another rectangular shield excavating machine, there is disclosed a rectangular shield excavating machine using excavating means composed of a drum disposed on a front portion of a quadrangularly tubular shield body so as to be capable of being rotated around an axis extending in the direction crossing an axis of the body and a large number of cutter bits mounted on the outer peripheral surface of the drum. (See Japanese Patent Public Disclosure (KOKAI) No. 2-66295) This excavating machine excavates a facing by the rotary motion of each cutter bit with the rotary motion of the drum.
However, since neither of these excavating machines known per se can drain large gravels contained in an excavated matter, the ground containing the large gravels cannot be excavated by such excavating machines.